The principal objectives of the proposed research are (1) to extend present knowledge of the epidemiology of unilocular hydatid disease (Echinococcus granulosus infection) in the western United States, specifically to more completely define its geographical distribution and host range and the circumstances associated with its transmission to animals and people and (2) to devise a suitable surveillance program for the infection and the local control procedures which should be applied to disclosed hydatid disease transmission sites in the western United States. Objective (1) will be accomplished by further hospital surveys, by epidemiological studies of wildlife involvement and of infections in hunting and herding dogs, by additional studies of transmission foci through the follow-up of infected sheep and of human cases, and by carrying out intensive studies in selected counties. In meeting objective (2), studies will be continued of the successful hydatid disease control programs of New Zealand and Tasmania and the developing program in Uruguay, with the analysis of epidemiological data for identification of factors possibly responsible for high and low rates of control progress. These results will be related to the assessed situation in the western United States and efforts continued to devise and have implemented a realistic surveillance program for hydatid disease in U.S. In addition, during epidemiological follow-up of human cases suspected of being autochthonous to California and adjacent states, procedures will be tested for the education of patients, families and other persons at unusual risk, for the diagnosis and treatment of dogs on infected premises, and for appropriate methods to recommend for dog feeding and handling and for the disposal of sheep and deer viscera.